As known, the presence of an electromagnetic field causes the appearance of voltages in electronic components or circuits, which voltages may cause burn-out and destruction of the components. A protection is thus needed against these parasitic voltages and is the more difficult to establish, the more the field in question is liable to appear suddenly with a short rise time which may reach some ten nanoseconds in particular cases, which for example represents the case of the aforesaid EMP.
It is known that a protection of this kind may be effected by enclosing the circuit or component to be protected within a shield or Faraday cage. However, this protection proves inadequate because these components or circuits necessarily have electrical connections with the outside, which form antenna in the presence of an extraneous field and permit penetration of parasitic charges into the element which is to be protected.